A. L. Ivanovskiĭ

Elastic parameters of single-crystal and polycrystalline wurtzite-like oxides BeO and ZnO: Ab initio calculations

The structural and elastic parameters (elastic constants; bulk, shear, and Young’s moduli; Poisson’s ratios; and Lamé coefficients) for ideal wurtzite-like beryllium and zinc monoxides are calculated by the full-potential linearized augmented-plane-wave (FLAPW) method with the WIEN2k code. These parameters are approximated to those for polycrystalline oxides BeO and ZnO in the framework of the Voigt-Reuss-Hill model. The results of calculations are compared with the available experimental data and used to estimate numerically the velocities of sound and the Debye temperatures for BeO and ZnO polycrystals.

Band structure, elastic and magnetic properties, and stability of antiperovskites MCNi3(M = Y − Ag) according to FLAPW-GGA calculations

Using the full-potential linearized augmented plane wave method (FLAPW) and the WIEN2k software package, calculations of the band structure and the elastic and magnetic properties of the ternary antiperovskite carbides MCNi3, where M = Y, Zr, ..., Ag (overall, nine compounds) are performed and the features of interatomic interactions in them are considered. Stability of these antiperovskite compounds depending on the 4d metal is discussed based on the calculated energies of formation of MCNi3 from the corresponding elements (according to the formal reaction M + C + 3Ni → MCNi3), and the conclusion is drawn that the YCNi3, ZrCNi3, and PdCNi3 antiperovskites can be synthesized. The obtained results are compared with the available data on known isostructural nickel-based carbides (antiperovskites MgCNi3, ZnCNi3).

Electronic and elastic properties of the superconducting nanolaminate Ti2InC

The electronic properties and elastic parameters of the superconducting nanolaminate Ti2InC are analyzed using the ab initio full-potential linearized augmented-plane-wave (FLAPW) method with the generalized gradient approximation (GGA) of the local spin density. The equilibrium parameters of the crystal lattice, the band structure, the total and partial densities of states, and the Fermi surface are determined within a unified approach. The independent elastic constants, the bulk modulus, and the shear modulus are calculated, and the elastic parameters are numerically estimated for the first time for polycrystalline Ti2InC.

Band Structure and Properties of Polymorphic Modifications of Lower Tungsten Carbide W 2 C

The structural and electronic properties are investigated and the relative stabilities of all the known polymorphic modifications (α, β, γ, ɛ) of the lower tungsten carbide W2C are numerically estimated using the ab initio full-potential linearized augmented plane wave (FLAPW) method within the generalized gradient approximation (GGA) of the local spin density. The equilibrium parameters of the crystal lattices, the band structures, and the total and partial densities of states are determined for the first time within a unified approach. The energies of formation of the α, β, γ, and ɛ polymorphic modifications of the lower tungsten carbide [in the reactions W2C ↔ 2W + C (graphite)] are calculated and used to discuss their relative stabilities.

Magnetic properties and electronic structure of the LaGaO3 perovskite doped with nickel

Solid solutions of the composition LaGa1 − xNixO3 (0.01 ≤ x ≤ 0.10) are synthesized, and their magnetic and electrical properties are investigated. It is established that the ground state of the Ni(III) atoms is the low-spin state 2Eg; however, in the temperature range under investigation, there occurs the 2Eg ⇆ 4T1g spin equilibrium. An increase in the nickel concentration leads to an increase in the electron conduction of the solid solutions. The band structure of the LaGa0.5Ni0.5O3 model compound is calculated using the ab initio full-potential linearized augmented-plane-wave method within the generalized gradient approximation (FLAPWGGA). It is shown that the dominant role in the variations observed in the magnetic and electrical properties of the nonmagnetic semiconductor LaGaO3 upon doping with nickel is played by the Ni 3d(eg↑, ↓) states.

Effect of chromium on the electronic structure of the cementite Fe3C

The effect of alloying of the cementite Fe3C with chromium on the band structure, atomic interactions, electric field gradients, and asymmetry parameters for iron nuclei is investigated using the self-consistent full-potential linear muffin-tin orbital (FPLMTO) method. An increase in the cohesive energy for the Fe3C-Cr system indicates an enhancement of the atomic interactions in the lattice of the cementite alloyed with chromium. It is found that the substitution of chromium for iron in the FeII positions containing eight equivalent iron atoms is energetically most favorable.

Effect of spin-orbit coupling on structural, electronic, and mechanical properties of cubic thorium monocarbide ThC

The effect of spin-orbit coupling (SOC) on the calculated structural, electronic, and mechanical properties of cubic ThC has been studied using the ab initio FLAPW-GGA method. It has been found that the inclusion of SOC hardly affects the calculated structural parameters of ThC. The inclusion of SOC becomes most important for theoretical description of quasi-core Th 6p states. A considerably weaker effect is exerted by SOC on the composition, the energy distribution of near-Fermi valence bands, the calculated energies of ThC formation, and the calculated elasticity parameters, i.e., the elastic constants Cij, the bulk modulus, and the shear modulus.

Elastic properties of carbide, nitride, and boride ceramics with WC-type structures

The elastic constants (Cij) of boride, carbide, and nitride (RuB, WC, WN, and TaN) ceramics with WC-type structures have been calculated using the full-potential linearized augmented plane wave (FLAPW) method with an exchange-correlation potential in the generalized gradient approximation (GGA). Numerical estimates of elastic parameters of the corresponding polycrystalline ceramics (bulk compression modulus, shear modulus, Young’s modulus, Poisson’s ratio, and Lamé’s coefficients) of these ceramics are obtained and analyzed for the first time.

Effect of electron correlations on the electronic structure and magnetic properties of the perovskite-like high-pressure phase ErCu3V4O12

The electronic structure and magnetic properties of double perovskite ErCu3V4O12 have been investigated in the framework of the projector augmented-wave method. It has been shown that the electron correlations play an important role: the calculations in the one-electron approximation predict that the ground state of ErCu3V4O12 is a magnetic metallic state, while with the inclusion of electron-electron correlations, it is a ferrimagnetic semimetallic state. It has been found that the magnetic Cu-Cu and V-V couplings are ferromagnetic and that the Cu-V magnetic coupling is antiferromagnetic.

Simulation of the structural, electronic, and magnetic properties of Fe3C1−x Bx borocementites

The structural, electronic, and magnetic properties and the enthalpy of formation of iron borocementites Fe3C1−xBx (x= 0, 0.25, 0.50, 0.75, 1.00) are analyzed using ab initio calculations in the framework of the electron density functional theory. It is found that the unit cell parameter a of the orthorhombic lattice increases linearly and the parameters b and c decrease as the boron concentration increases. The density of states at the Fermi level changes only slightly, and the main variations in the band structure occur in the region of the bottom of the valence bands. The magnetic moment of the iron atoms and the total magnetization and stability of the Fe3C1−xBx phases increase linearly with an increase in the boron concentration.